The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid vehicle systems typically utilize one or more electric, permanent magnet machines (e.g., electric drive) as part of a transmission system that provides a propulsion source to complement the engine. The accuracy of the manufacture, service and operation of these machines to produce specified torque profiles is important to the consistent and efficient operation of the vehicle.
Electric machines can be constrained in their torque capability at high speeds, due to operating voltage limits. At a given operating speed of the electric machine, the torque profile begins to decrease as the operating speed of the electric machine increases.
It is known, for example, to utilize flux weakening between a stator and a rotor of the electric machine to extend the operating speed range. It is further known to switch between coils wound to the stator to enable a two mode, series and parallel connection.
It is desirable to cover mode switching between a plurality of operating speed ranges of the electric drive to optimize the torque output of the torque profile as the operating speed increases. Likewise, it would be desirable to apply a method of scalability according to the number of speed ranges or modes desired and the number of phase winding circuits utilized.